Clinical and genomic insights into circulating tumor DNA-based alterations across the spectrum of metastatic hormone-sensitive and castrate-resistant prostate cancer

Background: Metastatic prostate cancer is a clonally heterogeneous disease state characterized by progressive somatic perturbations. The aim of this study was to identify cell free DNA- (cfDNA-) based alterations and their associations with outcomes in progressive metastatic prostate cancer.

Methods: In this longitudinal prospective cohort study plasma cfDNA/circulating tumor DNA (ctDNA) was analyzed before, during, and after androgen deprivation therapy (ADT) in 4 independent patient groups ranging from untreated metastatic hormone sensitive prostate cancer (mHSPC) to metastatic castrate resistant prostate cancer (mCRPC). Next generation sequencing was performed on ctDNA and germline DNA to characterize alterations and associations with clinical outcomes were determined for each group.

Findings: cfDNA yields were different in progressive mHSPC and mCRPC states (P < .001). In mHSPC, a higher than median ctDNA fraction was predictive of shorter time to ADT failure (HR, 2.29 [95% CI, 1.13-4.65]; Log-Rank P = .02). cfDNA, ctDNA taken with volume of metastatic disease in mHSPC and with alkaline phosphatase levels prognosticated survival better than clinical factors alone in mHSPC and mCRPC states (Log Rank P = 0.03). ctDNA-based AR, APC mutations were increased in mCRPC compared to mHSPC (P < ·05).TP53 mutations, RB1 loss, and AR gene amplifications correlated with poorer survival in mCRPC. Mutations in multiple DNA repair genes (ATM, BRCA1, BRCA2, CHEK2) were associated with time to ADT treatment failure and survival in mHSPC.

Interpretation: ctDNA fraction can further refine clinical prognostic factors in metastatic prostate cancer. Somatic ctDNA alterations have potential prognostic, predictive, and therapeutic implications in metastatic prostate cancer management.

Funding: Several funding sources have supported this study. A full list is provided in the Acknowledgments. No funding was received from Predicine, Inc. during the conduct of the study.